When using cost-per-acquisition (CPA) bidding, an advertiser bids using a maximum CPA and pays by:

Conversion

Click

Viewthrough

Impression

The correct Answer is:

Click

Explanation: Target CPA bidding uses your conversion tracking data to avoid unprofitable clicks and get more conversions at a lower cost. Based on your campaign’s history of conversions, Target CPA bidding automatically finds the optimal cost-per-click (CPC) bid for your ad each time it’s eligible to appear. It sets higher CPC bids for more valuable clicks and lower CPC bids for less valuable clicks.